U.S. patent application number 14/453900 was filed with the patent office on 2015-02-12 for driving device of multi-phase motor, driving method, cooling device, and electronic apparatus.
The applicant listed for this patent is ROHM CO., LTD.. Invention is credited to Toshiya SUZUKI.
Application Number | 20150042251 14/453900 |
Document ID | / |
Family ID | 52448057 |
Filed Date | 2015-02-12 |
United States Patent
Application |
20150042251 |
Kind Code |
A1 |
SUZUKI; Toshiya |
February 12, 2015 |
DRIVING DEVICE OF MULTI-PHASE MOTOR, DRIVING METHOD, COOLING
DEVICE, AND ELECTRONIC APPARATUS
Abstract
A driving device of a multi-phase motor having a plurality of
coils is provided. The driving device includes a back electromotive
force (BEMF) detecting comparator connected to one of the plurality
of coils to compare BEMF generated in one end of the one of the
plurality of coils with a midpoint voltage of the plurality of
coils and generate a BEMF detection signal, when the multi-phase
motor starts to be driven; and an initial state detecting unit
configured to detect a rotation state of the multi-phase motor
based on the BEMF detection signal and a hall detection signal.
Inventors: |
SUZUKI; Toshiya; (Kyoto,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ROHM CO., LTD. |
Kyoto |
|
JP |
|
|
Family ID: |
52448057 |
Appl. No.: |
14/453900 |
Filed: |
August 7, 2014 |
Current U.S.
Class: |
318/400.11 |
Current CPC
Class: |
H02P 6/20 20130101; H02P
6/16 20130101 |
Class at
Publication: |
318/400.11 |
International
Class: |
H02P 6/20 20060101
H02P006/20; H02P 6/16 20060101 H02P006/16 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 7, 2013 |
JP |
2013-164426 |
Claims
1. A driving device of a multi-phase motor having a plurality of
coils, the driving device comprising: a back electromotive force
(BEMF) detecting comparator connected to one of the plurality of
coils to compare BEMF generated in one end of the one of the
plurality of coils with a midpoint voltage of the plurality of
coils and generate a BEMF detection signal indicating a comparison
result, when the multi-phase motor starts to be driven; and an
initial state detecting unit configured to detect a rotation state
of the multi-phase motor based on the BEMF detection signal and a
hall detection signal corresponding to a result of comparing a pair
of hall signals indicating a position of a rotor of the multi-phase
motor, when the multi-phase motor starts to be driven.
2. The driving device of claim 1, wherein the initial state
detecting unit is configured to determine whether the multi-phase
motor idly rotates in a forward direction or in a reverse direction
based on a phase relationship between the hall detection signal and
the BEMF detection signal, when the multi-phase motor starts to be
driven.
3. The driving device of claim 2, wherein the initial state
detecting unit comprises: a first counter configured to measure a
first time duration comprising at least one of (i) a time duration
from a first edge that is one of a positive edge and a negative
edge of a predetermined signal selected from the BEMF detection
signal and the hall detection signal to a second edge that is a
subsequent edge, that comes after the first edge and is one of a
positive edge and a negative edge of the other signal different
from the predetermined signal selected from the BEMF detection
signal and the hall detection signal, and (ii) a time duration from
a third edge that is the other edge of the predetermined one signal
to a fourth edge that is the other edge, that comes after the third
edge, of the other signal; a second counter configured to measure a
second time duration comprising at least one of (iii) a time
duration from the second edge to the third edge, and (iv) a time
duration from the fourth edge to a fifth edge that comes after the
fourth edge and is one of the positive edge and the negative edge
of the predetermined one signal; and a determining unit configured
to determine whether the multi-phase motor idly rotates in the
forward direction or in the reverse direction, based on a magnitude
relationship between the first time duration measured by the first
counter and the second time duration measured by the second
counter.
4. The driving device of claim 3, wherein when the first time
duration and the second time duration are measured by the first
counter and the second counter, respectively, the determining unit
determines whether the multi-phase motor idly rotates in the
forward direction or in the reverse direction.
5. The driving device of claim 2, wherein the initial state
detecting unit comprises: a timing generating unit configured to
generate a strobe signal asserted in synchronization with a
predetermined one of the BEMF detection signal and the hall
detection signal; and a determining unit configured to determine
whether the multi-phase motor idly rotates in the forward direction
or in the reverse direction based on a level of the other signal of
the BEMF detection signal and the hall detection signal at a timing
at which the strobe signal is asserted.
6. The driving device of claim 2, wherein the initial state
detecting unit comprises: a period measuring unit configured to
measure a period of a predetermined one signal of the BEMF
detection signal and the hall detection signal and generate a
reference time duration proportional to the period; a first counter
configured to measure a first time duration comprising at least one
of (i) a time duration from a first edge that is one of a positive
edge and a negative edge of the predetermined signal selected from
the BEMF detection signal and the hall detection signal to a second
edge that comes after the first edge and is one of a positive edge
and a negative edge of the other signal different from the
predetermined signal selected from the BEMF detection signal and
the hall detection signal, and (ii) a time duration from a third
edge that is the other edge of the predetermined signal to a fourth
edge that is the other edge, that comes after the third edge, of
the other signal; and a determining unit configured to determine
whether the multi-phase motor idly rotates in the forward direction
or in the reverse direction, based on a magnitude relationship
between the first time duration measured by the first counter and
the reference time duration.
7. The driving device of claim 1, wherein the initial state
detecting unit is configured to determine that the multi-phase
motor has an error when a level of a predetermined signal selected
from the hall detection signal and the BEMF detection signal is
different from an expected value, at a timing of a predetermined
edge of the other signal different from the predetermined signal
selected from the hall detection signal and the BEMF detection
signal.
8. The driving device of claim 1, wherein the initial state
detecting unit is configured to determine that the multi-phase
motor is in a stopped state when an edge of the hall detection
signal is not detected for a predetermined period of time.
9. The driving device of claim 1, wherein the initial state
detecting unit is configured to determine that the multi-phase
motor is in a stopped state when an edge of the BEMF detection
signal is not detected for a predetermined period of time.
10. The driving device of claim 3, wherein the initial state
detecting unit is configured to determine that the multi-phase
motor is in a stopped state when the first time duration and the
second time duration are not measured for a predetermined period of
time.
11. The driving device of claim 1, further comprising a hall
comparator configured to compare the pair of hall signals
indicating the position of the rotor of the multi-phase motor from
a hall element and generate the hall detection signal.
12. The driving device of claim 1, wherein the multi-phase motor is
a fan motor.
13. A cooling device, comprising: a multi-phase fan motor; and a
driving device according to claim 1 configured to drive the
multi-phase fan motor.
14. An electronic apparatus comprising a cooling device according
to claim 13.
15. A driving method of a multi-phase motor having a plurality of
coils, the driving method comprising: comparing back electromotive
force (BEMF) generated in one end of one of the plurality of coils
with a midpoint voltage of the plurality of coils to generate a
BEMF detection signal indicating a comparison result, when the
multi-phase motor starts to be driven; and generating a pair of
hall signals indicating a position of a rotor of the multi-phase
motor by a hall element; comparing the pair of hall signals to
generate a hall detection signal; and detecting a rotation state of
the multi-phase motor based on the BEMF detection signal and the
hall detection signal, when the multi-phase motor starts to be
driven.
16. The driving method of claim 15, wherein the detecting a
rotation state of the multi-phase motor comprises determining
whether the multi-phase motor idly rotates in a forward direction
or in a reverse direction based on a phase relationship between the
hall detection signal and the BEMF detection signal, when the
multi-phase motor starts to be driven.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Applications No. 2013-164426, filed
on Aug. 7, 2013, the entire contents of which are incorporated
herein by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to a technique of driving a
multi-phase motor.
BACKGROUND
[0003] As a demand for faster operating speed for personal
computers and workstations has been increasing in recent years,
there has been an increasing effort to achieve faster operating
speed of a large scale integrated (LSI) circuit for computation
such as a central processing unit (CPU) or a digital signal
processor (DSP). Faster operating speed, i.e., a clock frequency,
of such an LSI leads to an increase in a heating amount produced by
the LSI. Such heating of the LSI may result in thermal runaway and
affect surrounding circuits
[0004] An example of a technique for cooling an LSI is an air
cooling method using a cooling fan. In this method, for example, a
cooling fan is disposed to face a surface of the LSI and blows
cooling air to the surface of the LSI.
[0005] In many cases, a 3-phase brushless DC motor is used as a
cooling fan. The 3-phase brushless DC motor (hereinafter, referred
to simply as a "fan motor") is controlled by detecting a position
of a rotor of the fan motor and sequentially changing conduction
phases based on the position of the rotor.
[0006] As methods of driving a fan motor, a method of driving a fan
motor using a hall sensor and a method of driving a fan motor using
back electromotive force generated by a coil of the fan motor have
been known. The driving method using a hall sensor is advantageous
in that a position of a rotor can be accurately detected but
disadvantageous in that the cost is increased due to the hall
sensor. Further, a fan motor cannot be properly controlled when
there is an error in operating the hall sensor.
[0007] The driving method using back electromotive force does not
require a hall sensor, resulting in a low cost. Further, the
driving method using the back electromotive force resolves
shortcomings that a fan motor cannot be controlled in case of an
error of a hall sensor. In this method, however, in order to detect
the back electromotive force, voltage applied to a coil needs to be
stopped during a non-conduction period including a timing at which
a zero-crossing occurs to maintain a high impedance state. A
driving waveform of a fan motor may be distorted due to the
non-conduction period. This may lead to a noise.
[0008] A device for driving a fan motor may need to drive the fan
motor with an appropriate sequence based on a state of the fan
motor when the fan motor starts to be driven after power is
supplied. That is, when the fan motor starts to drive, the fan
motor may be in a stopped state, a forward idle rotation state in
which the fan motor is idly rotating in a forward direction due to
rotational inertia of a previous driving state of the fan motor, or
a reverse idle rotation state in which the fan motor is idly
rotating in a reverse direction due to a wind from the outside.
[0009] Thus, the device for driving a fan motor is required to have
a function of detecting a state of a fan motor when the fan motor
starts to be driven. This function may also be required in a
multi-phase brushless DC motor, as well as in a fan motor.
SUMMARY
[0010] The present disclosure provides some embodiments of a device
for driving a sensorless motor capable of accurately determining a
state of the sensorless motor when the sensorless motor starts to
be driven.
[0011] A certain aspect of the present disclosure relates to a
device for driving a multi-phase motor. The driving device
includes: a back electromotive force (BEMF) detecting comparator
connected to one of the plurality of coils to compare BEMF
generated in one end of the one of the plurality of coils with a
midpoint voltage of the plurality of coils to generate a BEMF
detection signal indicating a comparison result, when the
multi-phase motor starts to be driven; and an initial state
detecting unit configured to detect a rotation state of the
multi-phase motor based on the BEMF detection signal and a hall
detection signal corresponding to a result of comparing a pair of
hall signals indicating a position of a rotor of the multi-phase
motor, when the multi-phase motor starts to be driven.
[0012] According to this aspect, a state when a multi-phase motor
starts to be driven can be detected.
[0013] The initial state detecting unit may be configured to
determine whether the multi-phase motor idly rotates in a forward
direction or in a reverse direction based on a phase relationship
between the hall detection signal and the BEMF detection signal,
when the multi-phase motor starts to be driven.
[0014] When a rotor idly rotates in a forward direction and when a
rotor idly rotates in a reverse direction, a phase relationship
between the hall detection signal and the BEMF detection signal is
reversed. Thus, a direction of idle rotation can be detected based
on phases of the hall detection signal and the BEMF detection
signal.
[0015] The initial state detecting unit may include: a first
counter configured to measure a first time duration including at
least one of (i) a time duration from a first edge that is one of a
positive edge and a negative edge of a predetermined signal
selected from the BEMF detection signal and the hall detection
signal to a second edge, that comes after the first edge and is one
of a positive edge and a negative edge of the other signal
different from the predetermined signal selected from the BEMF
detection signal and the hall detection signal, and (ii) a time
duration from a third edge that is the other edge of the
predetermined signal to a fourth edge that is the other edge, that
comes after the third edge, of the other signal; a second counter
configured to measure a second time duration including at least one
of (iii) a time duration from the second edge to the third edge and
(iv) a time duration from the fourth edge to a fifth edge, that
comes after the fourth edge and is one of the positive edge and the
negative edge of the predetermined signal; and a determining unit
configured to determine whether the multi-phase motor idly rotates
in a forward direction or in a reverse direction, based on a
magnitude relationship between the first time duration measured by
the first counter and the second time duration measured by the
second counter.
[0016] When the first time duration and the second time duration
are measured by the first counter and the second counter,
respectively, the determining unit may be configured to determine
whether the multi-phase motor idly rotates in a forward direction
or in a reverse direction.
[0017] In this case, such determination can be made within a
shortest period of time.
[0018] The initial state detecting unit may include: a timing
generating unit configured to generate a strobe signal asserted in
synchronization with a predetermined one of the BEMF detection
signal and the hall detection signal; and a determining unit
configured to determine whether the multi-phase motor idly rotates
in a forward direction or in a reverse direction based on a level
of the other signal of the BEMF detection signal and the hall
detection signal at a timing at which the strobe signal is
asserted.
[0019] The initial state detecting unit may be configured to
determine that the multi-phase motor has an error when a level of a
predetermined signal of the hall detection signal and the BEMF
detection signal is different from an expected value, at a timing
of a predetermined edge of the other signal of the hall detection
signal and the BEMF detection signal.
[0020] The initial state detecting unit may be configured to
determine that the multi-phase motor is in a stopped state when an
edge of the hall detection signal is not detected for a
predetermined period of time.
[0021] The initial state detecting unit may be configured to
determine that the multi-phase motor is in a stopped state when an
edge of the BEMF detection signal is not detected for a
predetermined period of time.
[0022] The initial state detecting unit may be configured to
determine that the multi-phase motor is in a stopped state when the
first time duration and the second time duration are not measured
for a predetermined period of time.
[0023] The multi-phase motor may be a fan motor.
[0024] Another aspect of the present disclosure relates to a
cooling device. The cooling device may include: a multi-phase fan
motor; and any driving device described above for driving the
multi-phase fan motor.
[0025] Yet another aspect of the present disclosure relates to an
electronic apparatus. The electronic apparatus may include the
cooling device described above.
[0026] Also, it is effective that any combination of the above
components may be made, or the components or expressions of the
present disclosure may be substituted by each other, as aspects of
the present disclosure, among the method, apparatus, system, and
the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a block diagram illustrating an electronic
apparatus including a cooling device according to an embodiment of
the present disclosure.
[0028] FIGS. 2A and 2B are operational waveform views in cases of a
forward idle rotation and a reverse idle rotation.
[0029] FIG. 3 is a block diagram illustrating a configuration
example of an initial state detecting unit.
[0030] FIGS. 4A and 4B are views illustrating operations of the
initial state detecting unit of FIG. 3.
[0031] FIG. 5A is a block diagram and FIG. 5B is an operational
waveform view of an initial state detecting unit according to a
second modified example.
[0032] FIG. 6A is a block diagram and FIG. 6B is an operational
waveform view of an initial state detecting unit according to a
third modified example.
DETAILED DESCRIPTION
[0033] Some embodiments of the present disclosure will now be
described in detail with reference to the drawings. Throughout the
drawings, the same or similar elements, members and processes are
denoted by the same reference numerals and explanation of which
will not be repeated. The disclosed embodiments are provided for
the purpose of illustration of the present disclosure, and the
present disclosure is not limited to the features and combinations
thereof described in the embodiments of the present disclosure and
the embodiments alone cannot be necessarily construed to describe
the spirit of the present disclosure.
[0034] In the present disclosure, the phrase "a connection of a
member A and a member B" is intended to include a direct physical
connection of the member A and the member B as well as an indirect
connection thereof via other member as long as the other member has
no substantial effect on the electrical connection of the member A
and the member B or has no damage to functions and effects shown by
a combination of the member A and the member B. Similarly, the
phrase "an interposition of a member C between a member A and a
member B" is intended to include a direct connection of the member
A and the member C or a direct connection of the member B and the
member C as well as an indirect connection thereof via other member
as long as the other member has no substantial effect on the
electrical connection of the member A, the member B and the member
C or has no damage to functions and effects shown by a combination
of the member A, the member B and the member C.
[0035] FIG. 1 is a block diagram illustrating an electronic
apparatus 100 including a cooling device 200 according to an
embodiment of the present disclosure. The electronic apparatus 100
may be a calculator such as a personal computer or a workstation,
or a home appliance such as a refrigerator or a television, and
include a cooling target, for example, a CPU 102. The cooling
device 200 cools the CPU 102 by blowing air onto the CPU 102.
[0036] The cooling device 200 includes a fan motor 202, a hall
element 204, and a driving device 300. The fan motor 202 is a
3-phase brushless DC motor and disposed in proximity to the CPU 102
which is a cooling target. The driving device 300 drives the fan
motor 202 based on a control input signal (hereinafter, referred to
simply as a "control signal") S1 for indicating a torque (or
revolutions per minute (RPM)) of the fan motor 202. The cooling
device 200 may be modularized to be commercially sold or
distributed.
[0037] The fan motor 202 includes a star-connected U-phase coil
L.sub.U, a V-phase coil L.sub.U, and an L-phase coils L.sub.W and a
permanent magnet (not shown). The hall element 204 is installed in
a predetermined location of the fan motor 20 and generates a pair
of hall signals VH+ and VH- indicating positions of a rotor of the
fan motor 202. A hall bias voltage V.sub.HB is supplied from the
driving device 300 to the hall element 204. In the cooling device
200 according to this embodiment, it should be noted that the hall
element 204 is prepared only for one phase, rather than for all
three phases of the fan motor 202.
[0038] The driving device 300 may be a functional integrated
circuit (IC) integrated on a single semiconductor substrate. A
source voltage Vcc is applied to a power terminal VCC, and a ground
voltage is supplied to a ground terminal GND. Further, output
terminals OUTU, OUTV and OUTW of the driving device 300 are
connected to one ends of the coils L.sub.U, L.sub.V and L.sub.W of
the fan motor 202, respectively, and a midpoint voltage Vcom of the
fan motor 202 is input to a common terminal COM.
[0039] The driving device 300 includes a back electromotive force
(BEMF) detecting comparator 302, a hall comparator 304, an initial
state detecting unit 306, a driving signal synthesizing unit 308, a
PWM signal generating unit 310, a driving circuit 312, and a hall
bias (HB) power source 314.
[0040] The HB power source 314 generates a hall bias (HB) voltage
V.sub.HB and supplies the generated HB voltage V.sub.HB to the hall
element 204.
[0041] The PWM signal generating unit 310 receives a control signal
S1 for indicating a torque (or revolutions per minute (RMP)) of the
fan motor 202 from the outside, and generates a pulse width
modulation (PWM) signal S2 that is pulse modulated based on the
control signal S1. A duty ratio of the PWM signal S2 is varied
depending on the control signal S1. Alternatively, a control signal
S1 that is pulse width-modulated based on a target torque of the
fan motor 202 may be input from the outside of the driving device
300 and then output as a PWM signal S2. Alternatively, the PWM
signal generating unit 310 may receive an analog voltage depending
on an ambient temperature Ta obtained using a thermistor (not
shown) or the like, and generate a PWM signal S2 having a duty
ratio corresponding to the analog voltage. Alternatively, the PWM
signal generating unit 310 may receive a digital signal indicating
a duty ratio from a host processor such as a CPU, and generate a
PWM signal S2 depending on the digital signal.
[0042] The BEMF detecting comparator 302 is connected to one of the
plurality of coils L.sub.U to L.sub.W, for example, the coil
L.sub.U in this embodiment. When the cooling device 200 starts,
i.e., when the fan motor 202 starts to be driven, the BEMF
detecting comparator 302 compares a voltage V.sub.U generated in
one end of the coil L.sub.U with a midpoint voltage Vcom of the
plurality of coils L.sub.U to L.sub.W to generate a BEMF detection
signal S3 indicating a comparison result. In this case, since the
BEMF detecting comparator 302 compares the voltages before the
conduction is started by the driving circuit 312, the voltage
V.sub.U at one end of the coil L.sub.U corresponds to BEMF.
[0043] The hall comparator 304 compares the pair of hall signals
VH+ and VH- from the hall element 204 to generate a hall detection
signal S4. For example, in case of VH+>VH-, the hall detection
signal S4 has a high level, and in case of VH+<VH-, the hall
detection signal S4 has a low level.
[0044] The hall detection signal S4 is supplied to the initial
state detecting unit 306 and the driving signal synthesizing unit
308. The driving signal synthesizing unit 308 receives the hall
detection signal S4 and the PWM signal S2, synthesizes them, and
generates driving control signals S5.sub.U, S5.sub.V, and S5.sub.W
for a U phase, a V phase, and a W phase, respectively.
Specifically, the driving signal synthesizing unit 308 controls a
current in synchronization with the hall detection signal S4 and
controls the torque of the fan motor 202 based on the PWM signal
S2. In addition, the driving signal synthesizing circuit 14 changes
a driving sequence of the fan motor 202 based on the detection
results from the initial state detecting unit 306 immediately after
power is supplied to the driving device 300.
[0045] The driving circuit 312 applies driving voltages V.sub.U,
V.sub.V, and V.sub.W to one ends of the respective coils L.sub.U,
L.sub.V, and L.sub.W depending on the driving control signals
S5.sub.U, S5.sub.V, and S5.sub.W. The driving circuit 312 may
PWM-drive (or switching-drive) the fan motor 202 or a bridged
transless (BTL)-drive the fan motor 202.
[0046] When PWM driving the fan motor 202, the driving voltages
V.sub.U, V.sub.V, and V.sub.W are switched between two values of
the source voltage Vcc and the ground voltage V.sub.GND so as to be
pulse width-modulated. A duty ratio of each of the driving voltages
V.sub.U, V.sub.V, and V.sub.W is determined based on target torque
(target RPM). Also, in order to suppress noise generated during
phase conversion, a duty ratio of each driving voltage is gently
changed in a phase shift period. The driving circuit 312 in case of
the PWM driving is configured as a 3-phase bridge circuit.
[0047] When BTL driving the fan motor 202, envelope curves of the
driving voltages V.sub.U, V.sub.V, and V.sub.W are gently shifted
between the source voltage Vcc and the ground voltage V.sub.GND. By
shifting the envelope curves of the driving voltages of the
respective phases based on a sine wave shape, a modified sine wave,
a trapezoid wave, and the like, the noise may be further reduced
than when PWM driving the fan motor 202. The waveforms of the
envelope curves may be generated with reference to a predetermined
table or may be generated based on the hall signals VH+ and VH-.
Driving voltages of respective phases may be pulse width-modulated
to have a duty ratio corresponding to target torque (target RPM).
The driving circuit 312 in case of BTL driving is configured to
include amplifiers installed in each of the U phase, the V phase,
and the W phase. An output terminal of each amplifier is configured
to have a push-pull form.
[0048] Also, the driving signal synthesizing unit 308 and the
driving circuit 312 may use a known technique and a configuration
and a driving method thereof are not particularly limited.
[0049] An RPM signal generating unit 316 generates an RPM signal FG
that transitions every 180 machine angle (motor angle) of the fan
motor 202, i.e., every half rotation of the fan motor 202, and
outputs the RPM signal FG from an FG terminal. The RPM signal
generating unit 316 generates the FG signal based on the hall
detection signal S4.
[0050] When the fan motor 202 starts to be driven, the initial
state detecting unit 306 detects a state (rotation state) of the
fan motor 202 based on the BEMF detection signal S3 and the hall
detection signal S4, generates a determination signal S6 indicating
detection results, and outputs the determination signal S6 to the
driving signal synthesizing unit 308. The driving signal
synthesizing unit 308 selects a start sequence corresponding to the
state of the fan motor 202 based on the determination signal S6
when the fan motor 202 starts to be driven.
[0051] The state of the fan motor 202 immediately after the fan
motor 202 starts to be driven may be one of the following three
states:
[0052] (1) Forward idle rotation state in which the fan motor 202
is idly rotating in a forward direction;
[0053] (2) Reverse idle rotation state in which the fan motor 202
is idly rotating in a reverse direction; and
[0054] (3) Stopped state.
[0055] When the fan motor 202 is in a stopped state at a start-up
(i.e., when the fan motor 202 starts to be driven), the driving
signal synthesizing unit 308 executes a normal start sequence
(3-phase start sequence). Further, when the fan motor 202 idly
rotates in a forward direction at a start-up, the driving signal
synthesizing unit 308 generates a driving control signal S5 in
synchronization with the hall detection signal S4 or the FG signal.
Also, when the fan motor 202 idly rotates in a reverse direction at
a start-up, the driving signal synthesizing unit 308 stops the fan
motor 202 based on a reverse rotation protecting process and then
executes the 3-phase start sequence. Also, in each state, the
details of the start sequence are not particularly limited and any
suitable known technique may be used.
[0056] FIGS. 2A and 2B are operational waveform views in cases of a
forward idle rotation and a reverse idle rotation.
[0057] A phase relationship between the hall detection signal S4
and the BEMF detection signal S3 is determined based on in which
phase the BEMF is detected and in which coil of the fan motor 202
the hall element 204 is to be disposed. FIGS. 2A and 2B are merely
illustrative. It should be noted that those illustrated in FIGS. 2A
and 2B are merely phase relationships between the BEMF detection
signal S3 based on the U-phase BEMF V.sub.U and the hall detection
signal S4 obtained by the hall element 204 disposed between the U
phase and the V phase.
[0058] As can be seen from FIGS. 2A and 2B, the hall detection
signal S4 and the BEMF detection signal S3 have a first phase
relationship in a forward idle rotation state and a second phase
relationship in a reverse idle rotation state. That is, the
magnitudes of a phase difference .PHI. of the BEMF detection signal
S3 for the hall detection signal S4 in cases of the forward idle
rotation state and the reverse idle rotation state are different.
Thus, when the fan motor 202 starts to be driven, the initial state
detecting unit 306 determines whether the fan motor 202 idly
rotates in a forward direction or in a reverse direction based on a
phase relationship between the BEMF detection signal S3 and the
hall detection signal S4.
[0059] FIG. 3 is a block diagram illustrating a configuration
example of the initial state detecting unit 306.
[0060] The initial state detecting unit 306 includes a first filter
320, a second filter 322, a first edge detecting unit 324, a second
edge detecting unit 326, a first counter 330, a second counter 332,
and a determining unit 334.
[0061] The first filter 320 and the second filter 322 remove noise
of the hall detection signal S4 and noise of the BEMF detection
signal S3, respectively. The first edge detecting unit 324 detects
an edge of the hall detection signal S4, and the second edge
detecting unit 326 detects an edge of the BEMF detection signal S3.
Here, it is assumed that the first edge detecting unit 324 detects
both a positive edge and a negative edge of the hall detection
signal S4 and the second edge detecting unit 326 detects both a
positive edge and a negative edge of the BEMF detection signal
S3.
[0062] The first counter 330 measures at least one of (i) a time
duration T1a from a first edge E1 (here, assumed as a positive
edge), that is one of a positive edge and a negative edge of a
predetermined signal (here, the hall detection signal S4) selected
from the BEMF detection signal S3 and the hall detection signal S4,
to a second edge E2 (here, a positive edge), that comes after the
first edge E1 and is one of a positive edge and a negative edge of
the other signal (here, the BEMF detection signal S3) different
from the predetermined signal selected from the BEMF detection
signal S3 and the hall detection signal S4, and (ii) a time
duration T1b from a third edge E3 that is the other edge (here, a
negative edge) and one of the positive and the negative edge of the
predetermined signal (here, the hall detection signal S4) to a
fourth edge E4 that is the other edge (here, a negative edge), that
comes after the third edge and one of the positive edge and the
negative edge, of the other signal (here, the BEMF detection signal
S3) different from the predetermined signal. In this embodiment,
the first counter 330 measures both of the two time durations T1a
and T1b.
[0063] The second counter 332 measures at least one of (iii) a time
duration T2a from the second edge E2 to the third edge E3 and (iv)
a time duration T2b from the fourth edge E4 to a fifth edge E5 that
is an edge (here, a positive edge), that comes after the fourth
edge E4, which may be the positive edge and the negative edge of
the predetermined signal (the hall detection signal S4). In this
embodiment, the second counter 332 measures both of the two time
durations T2a and T2b.
[0064] When an RPM of the fan motor 202 that idly rotates is
constant, it may be understood that the time durations T1a and T1b
measured by the first counter 330 are equal. Similarly, when the
RPM of the fan motor 202 that idly rotates is constant, it may be
understood that the time durations T2a and T2b measured by the
second counter 332 are also equal. Here, the time duration measured
by the first counter 330 is referred to as a first time duration T1
and the time duration measured by the second counter 332 is
referred to as a second time duration T2.
[0065] The determining unit 334 determines a phase relationship
between the BEMF detection signal S3 and the hall detection signal
S4 based on a magnitude relationship between the first time
duration T1 and the second time duration T2, and determines whether
the fan motor 202 idly rotates in a forward direction or in a
reverse direction.
[0066] The initial state detecting unit 306 may determine a stopped
state of the fan motor 202 based on at least one of the following
conditions:
[0067] (1) When an edge of the hall detection signal S4 is not
detected for a predetermined period of time;
[0068] (2) When an edge of the BEMF detection signal S3 is not
detected for a predetermined period of time; and
[0069] (3) When the first time duration T1 and/or the second time
duration T1 are not measured for a predetermined period of
time.
[0070] Further, at a timing of a predetermined edge (for example, a
positive edge) of a predetermined signal (for example, the hall
detection signal S4) selected from the hall detection signal S4 and
the BEMF detection signal S3, if a level of the other signal (i.e.,
the BEMF detection signal S3) different from the predetermined
signal is different from an expectation value, the initial state
detecting unit 306 determines that the operation has an error. When
the driving circuit 312 is operating normally, the BEMF detection
signal S3 should have a low level at a timing of the positive edge
of the hall detection signal S4 in both the forward idle rotation
and the reverse idle rotation, and thus, the expectation value is a
low level.
[0071] In the above, the configurations of the cooling device 200
and the driving device 300 have been described. Operations of the
cooling device 200 and the driving device 300 will now be
described.
[0072] FIGS. 4A and 4B are views illustrating operations of the
initial state detecting unit 306 of FIG. 3.
[0073] FIG. 4A illustrates an operation in case of the forward idle
rotation. At time t0, the initial state detecting unit 306 starts
its determining operation. At time t1, a first edge E1 is detected
and the first counter 330 measures an elapsed time T1a from the
first edge E1 to a next second edge E2. The second counter 332
measures an elapsed time T2a from the second edge E2 to a third
edge E3.
[0074] As illustrated in FIG. 4A, in case of the forward idle
rotation, T1 is smaller than T2 (T1<T2). Thus, in case of
T1<T2, the determining unit 334 determines that the fan motor
202 idly rotates in a forward direction.
[0075] FIG. 4B illustrates an operation in case of the reverse idle
rotation. At time t0, the initial state detecting unit 306 starts
its determining operation. At time t1, a first edge E1 is detected
and the first counter 330 measures an elapsed time T1a from the
first edge E1 to a next second edge E2. The second counter 332
measures an elapsed time T2a from the second edge E2 to a third
edge E3.
[0076] As illustrated in FIG. 4B, in case of the reverse idle
rotation, T2 is smaller than T1 (T2<T1). Thus, in case of
T2<T1, the determining unit 334 determines that the fan motor
202 idly rotates in a reverse direction.
[0077] After the first time T1 and the second time T2 are measured,
the determining unit 334 compares the first time T1 and the second
time T2 and determines an initial state of the fan motor 202.
[0078] For example, when the waveforms of FIG. 4A is generated, it
is assumed that the initial state detecting unit 306 starts its
determining operation before the edge E2 after the edge E1. In this
case, first, the second time duration T2a is measured by the second
counter 332 and then the first time duration T1b is measured by the
first counter 330. In this case, the determining unit 334 can
compare the second time duration T2a and the first time duration
T1b at a timing of the edge E3.
[0079] Alternatively, when the initial state detecting unit 306
starts its determining operation between the second edge E2 and the
third edge E3, the first time duration T1b is first measured by the
first counter 330 and then the second time duration T2b is measured
by the second counter 332. In this case, the determining unit 334
can compare the first time duration T1b and the second time
duration T2b at a timing of an edge E5.
[0080] In the above, the operations of the cooling device 200 and
the driving device 300 have been described.
[0081] In the driving device 300, when the fan motor 202 is
normally driven, a rotation state of the fan motor 202 is detected
using the hall detection signal S4, without using the BEMF
detection signal S3. Thus, a non-conduction period, which is
required for the conventional sensorless driving device using the
BEMF detection signal S3, is not necessary and a generation of
noise is not increased.
[0082] Further, a single hall element is satisfactory and cost
effective when compared to the conventional driving device in which
hall elements are installed in all of the phases U, V, and W,
respectively.
[0083] Also, in the driving device 300, a state of the fan motor
202 at the time when the fan motor 202 starts to be driven may be
detected by monitoring the BEMF detection signal S3 and the hall
detection signal S4. Thus, the fan motor 202 may be started based
on an appropriate sequence.
[0084] Also, the initial state detecting unit 306 of FIG. 3 enables
the first counter 330 to measure both the first time durations T1a
and T1b and the second counter 332 to measure both the second time
durations T2a and T2b. Accordingly, when the first time duration T1
and the second time duration T2 are measured one time,
respectively, the determining unit 334 may immediately determine
whether the fan motor 202 idly rotates in a forward direction or in
a reverse direction.
[0085] That is, if it is configured such that only the first time
duration T1a and the second time duration T2a are measured, when
the determining operation starts between the edges E1 and E2 of
FIG. 4A, it should wait for the next cycle to determine the
rotation state of the fan motor 202. In contrast, the determination
may be made within the shorter period of time at the timing of edge
E4 of FIG. 4A by using the initial state detecting unit 306 of FIG.
3.
[0086] In addition, an error of the driving device 300 may be
detected by an error detecting unit 336. That is, in each of the
forward idle rotation state and the reverse idle rotation state,
the hall element 204 needs to be appropriately positioned in
advance to obtain the waveforms illustrated in FIGS. 2A and 2B. If
the hall element 204 deviates from a predetermined position, phase
relationships between the hall detection signal S4 and the BEMF
detection signal S3 are changed to be different from those
illustrated in FIGS. 2A and 2B. Thus, an error resulting from a
position shift or the like of the hall element 204 may be detected
by checking a level of the other signal at a timing of an edge of
one signal by the error detecting unit 336.
[0087] In the above, the present disclosure has been described
based on the embodiment. It will be understood by a person skilled
in the art that this embodiment is illustrative and combinations of
respective components or respective processes may be variously
modified and such modified examples are also within the scope of
the present disclosure. Hereinafter, these modified examples will
be described.
First Modified Example
[0088] The initial state detecting unit 306 may determine a phase
relationship between the BEMF detection signal S3 and the hall
detection signal S4, and a determining algorithm and configuration
thereof are not limited to those of this embodiment. For example,
the first counter 330 and the second counter 332 may be configured
as a single counter. That is, a single counter may be used as the
first counter 330 and the second counter 332 to count up during the
first time duration T1 and count down during the second time
duration T2, so that the first time duration T1 and the second time
duration T2 may be compared based on a magnitude relationship
between a count value when the counting operation was completed and
an initial value when counting started.
Second Modified Example
[0089] FIG. 5A is a block diagram and FIG. 5B is an operational
waveform view of an initial state detecting unit 306a according to
a second modified example.
[0090] As illustrated in FIG. 5A, the initial state detecting unit
306a includes a timing generator 340 and a determining unit 342.
The timing generator 340 generates a strobe signal S7 asserted (for
example, high level) in synchronization with a predetermined signal
(here, the hall detection signal S4) selected from the BEMF
detection signal S3 and the hall detection signal S4. The
determining unit 342 determines whether the fan motor 202 idly
rotates in a forward direction or in a reverse direction based on a
level of the other signal (i.e., the BEMF detection signal S3)
different from the predetermined signal selected from the BEMF
detection signal S3 and the hall detection signal S4 at a timing at
which the strobe signal S7 is asserted.
[0091] As illustrated in FIG. 5B, the strobe signal S7 is generated
between a position of an edge E2a of the BEMF detection signal S3
(i) expected when the fan motor 202 idly rotates in a forward
direction and an edge Eb2 of the BEMF detection signal S3 (ii)
expected when the fan motor 202 idly rotates in a reverse
direction. For example, the timing generator 340 may measure a half
period Th of the hall detection signal S4 and assert the strobe
signal S7 after the lapse of .tau.=Th/2 from the positive edge of
the hall detection signal S4. Also, the time t is not limited to
Th/2 and may be any time that comes between the edges E2a and
E2b.
Third Modified Example
[0092] FIG. 6A is a block diagram and FIG. 6B is an operational
waveform view of an initial state detecting unit 306b according to
a third modified example.
[0093] The initial state detecting unit 306b includes a period
measuring unit 344, a first counter 330, and a determining unit
346. The period measuring unit 344 measures a half period Th (or a
full period) of a predetermined signal (here, assumed as the hall
detection signal S4) selected from the BEMF detection signal S3 and
the hall detection signal S4 to generate a reference time duration
Tref proportional to the half period Th. For example, the reference
time duration Tref may be half of the half period Th
(Tref=Th/2).
[0094] Similar to the first counter 330 of FIG. 3, the first
counter 330 measures a first time duration T1. The determining unit
346 determines whether the fan motor 202 idly rotates in a forward
direction or in a reverse direction based on a magnitude
relationship between the reference time duration Tref and the first
time duration T1. In this example, in case of T1<Tref, the
determining unit 346 may determine that the fan motor 202 idly
rotates in a forward direction, and in case of T1>Tref, the
determining unit 346 may determine that the fan motor 202 idly
rotates in a reverse direction. The reference time duration Tref is
not limited to Th/2 and may be set to have a value between the
first time duration T1 when the fan motor 202 idly rotates in a
forward direction and the second time duration T2 when the fan
motor 202 idly rotates in a reverse direction.
Fourth Modified Example
[0095] In the embodiment, the case in which the hall comparator 304
is integrated in the driving device 300 has been described, but the
present disclosure is not limited thereto and the hall comparator
304 may be installed outside of an IC of the driving device 300.
For example, a hall IC formed by integrating the hall comparator
304 and the hall element 204 may be used.
Fifth Modified Example
[0096] In the embodiment, the 3-phase fan motor 202 has been
described as an example, but the present disclosure is not limited
thereto and may be used for driving a multi-phase motor having a
plurality of coils.
Sixth Modified Example
[0097] In the embodiment, the case in which the cooling device 200
is installed in the electronic apparatus 100 to cool the CPU 102
has been described, but the purpose of the present disclosure is
not limited thereto and may be used for various applications for
cooling a heating element. More specifically, the purpose of the
driving device 300 according to this embodiment may be used to
drive various other motors, without being limited to the driving of
the fan motor 202.
[0098] According to the present disclosure, it is possible to
detect a state of a motor when it starts to be driven.
[0099] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the disclosures. Indeed, the novel
methods and devices described herein may be embodied in a variety
of other forms; furthermore, various omissions, substitutions and
changes in the form of the embodiments described herein may be made
without departing from the spirit of the disclosures. The
accompanying claims and their equivalents are intended to cover
such forms or modifications as would fall within the scope and
spirit of the disclosures.
* * * * *